feat: Add ICMP, DNS, and GraphQL monitor types

Add three new monitor types with full support:

- ICMP: Ping monitoring with configurable packet count, tracks packet
  loss and average RTT. Marks degraded on partial packet loss.

- DNS: DNS resolution monitoring supporting A, AAAA, CNAME, MX, and TXT
  records. Optional custom DNS server and validation of expected IPs/CNAME.

- GraphQL: GraphQL endpoint monitoring with query execution, variable
  support, error detection, and content validation.

All new monitors include retry support, response time tracking, and
integrate with existing display options (round_response_time, etc).

GraphQL monitors also support SSL certificate tracking.

1 files changed, 7 insertions, 1 deletions

diff --git a/internal/monitor/monitor.go b/internal/monitor/monitor.go
index f4a6f66..5ec283a 100644
--- a/internal/monitor/monitor.go
+++ b/internal/monitor/monitor.go
@@ -34,7 +34,7 @@ type Monitor interface {
 	// Name returns the monitor's name
 	Name() string
 
-	// Type returns the monitor type (http, https, tcp, gemini)
+	// Type returns the monitor type (http, https, tcp, gemini, icmp, dns, graphql)
 	Type() string
 
 	// Target returns the monitor target (URL or host:port)
@@ -68,6 +68,12 @@ func New(cfg config.MonitorConfig) (Monitor, error) {
 		return NewTCPMonitor(cfg)
 	case "gemini":
 		return NewGeminiMonitor(cfg)
+	case "icmp":
+		return NewICMPMonitor(cfg)
+	case "dns":
+		return NewDNSMonitor(cfg)
+	case "graphql":
+		return NewGraphQLMonitor(cfg)
 	default:
 		return nil, &UnsupportedTypeError{Type: cfg.Type}
 	}